package com.example.demo.nio;

import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.SocketChannel;
import java.util.Iterator;
import java.util.Set;

public class NHttpClient {


    public static void main(String[] args) throws Exception {


        Selector selector = Selector.open();
        InetSocketAddress remoteAddress = new InetSocketAddress("chushu.la", 80);
        // 调用open的静态方法创建连接指定的主机的SocketChannel
        SocketChannel socketChangel = SocketChannel.open(remoteAddress);
        // 设置该sc已非阻塞的方式工作
        socketChangel.configureBlocking(false);
        // 将SocketChannel对象注册到指定的Selector
        socketChangel.register(selector, SelectionKey.OP_READ);
        sendMessage(socketChangel, createHttpMsg());

        boolean remoteConnClosed = false;
        while (!remoteConnClosed) {
            int n = selector.select(1000*60);//设置超时为1分钟
            if (n <= 0) {
                break;//
            }
            Set<SelectionKey> selectedKeys = selector.selectedKeys();
            Iterator<SelectionKey> iter = selectedKeys.iterator();
            while (iter.hasNext()) {
                SelectionKey key = iter.next();
                if (key.isReadable()) {
                    ByteBuffer buffer = ByteBuffer.allocate(1024);//如果读取的数据大于1024, 则下次调用 selector.select 的数值还会大于0
                    SocketChannel client = (SocketChannel) key.channel();
                    int num = client.read(buffer);
                    while(num > 0){//如果num = 0, 表示读取不到远端数据，可能是远端网速慢或者其他网络原因， 下次selector.select返回时可再读; 如果num=-1,表示远端关闭了连接。
                        client.read(buffer);
                        String reString = new String(buffer.array(), "utf-8");
                        System.out.print(reString);
                        num = client.read(buffer);
                    }

                    if(num == -1){//远程连接主动关闭
                        System.out.println("remote server close connection~~");
                        client.close();
                        key.cancel();
                        remoteConnClosed = true;
                    }

                }
                //这里必须移除掉该selectionKey, 否则下次select调用时还会存在
                iter.remove();
            }

        }
    }

    private static String createHttpMsg() {
        StringBuffer sBuffer = new StringBuffer();
        sBuffer.append("GET / HTTP/1.1").append("\r\n");
        sBuffer.append("Host: chushu.la").append("\r\n");
//		sBuffer.append("Connection: Closed");
        sBuffer.append("Connection: keep-alive");
        sBuffer.append("\r\n").append("\r\n");
        return sBuffer.toString();
    }

    public static void sendMessage(SocketChannel client, String msg)throws Exception {
        ByteBuffer buffer = ByteBuffer.wrap(msg.getBytes());
        client.write(buffer);
    }
}
